One of the things I really like about Vaadin is the simplicity and the speed when developing the UI with Vaadin. Another great benefit of Vaadin is its Add-On directory where lots of useful add-ons are maintained and provided.
Add-Ons which implement client side UI must be recompiled by the GWT compiler to include them into your app.
To me it was not clear how to do that precisely despite the docs provided here and here.
To minimize compile time I recommend to use a maven profile as described in the article. This prevents a GWT compilation of the widgetset each time the project is built.
In my case I used version 2.3.0 for GWT and for the gwt-maven-plugin.